ESTRO 2024 - Abstract Book

S4894

Physics - Quality assurance and auditing

ESTRO 2024

Results:

For IMRT audits (n=34) the results for 3D gamma analysis at 3%,2mm criteria and 10% low dose threshold were (mean±SD) 97.9±4.5% (Range 81.0%-100.0%). Separation of the audit results according to EPID type (Varian aS1200, Varian aS1000, Elekta iView) gave results of 99.4±0.8% (n=7), 98.7±3.7% (n=19), and 94.7±6.5% (n=8) respectively. At this criterion, 30/33 audits passed at Optimal level and 3/33 audits failed at Action level. For IMRT, outliers were apparent for some systems identified as likely due to older EPID dosimetric performance problems as well as a potential TPS commissioning problem. For VMAT (n=36) the pass-rates were 98.4±2.3% (Range 91.6-100.0%). Separation of the audit results according to EPID type gave 99.5±0.7%, 97.3±2.8%, and 99.8±0.1% for aS1200, aS1000, and iView respectively. At this criterion, 32/36 audits passed at Optimal level and 4/36 passed at Tolerance level. No audits failed this criterion. The lower pass-rates were identified as most likely TPS related

Conclusion: